二分查找
java BinarySearch whitelist.txt < tinyT.txt
输出
50
99
13
whitelist.txt是BinarySearch 的参数,"<"大于号是将tinyT.txt作为输入流
public static int indexOf(int[] a, int key) {
int lo = 0;
int hi = a.length - 1;
while (lo <= hi) {
// Key is in a[lo..hi] or not present.
int mid = lo + (hi - lo) / 2;
if (key < a[mid]) hi = mid - 1;
else if (key > a[mid]) lo = mid + 1;
else return mid;
}
return -1;
}
public static void main(String[] args) {
// read the integers from a file
In in = new In(args[0]);
int[] whitelist = in.readAllInts();
// sort the array
Arrays.sort(whitelist);
// read integer key from standard input; print if not in whitelist
while (!StdIn.isEmpty()) {
int key = StdIn.readInt();
if (HelloWorld.indexOf(whitelist, key) == -1)
StdOut.println(key);
}
}